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The Forum is open to everyone, including students, visitors, and faculty members from all departments and institutes!

The 60 minute lecture is followed by a 10 minute break and a 30-60 minute discussion. The language of presentation is English or Hungarian.

The scope of the Forum includes all aspects of theoretical philosophy, including:

  • logic and philosophy of formal sciences
  • philosophy of science
  • modern metaphysics
  • epistemology
  • philosophy of language
  • problems in history of philosophy and history of science, relevant to the above topics
  • particular issues in natural and social sciences, important for the discourses in the main scope of the Forum.


6 March (Wednesday) 5:00 PM  Room 226
Mihály Makkai
Department of Mathematics and Statistics
McGill University, Toronto
This is the second lecture of Professor Makkai's lectures series on FOLDS:
      Lecture I      1 March, 4:15 PM, Room 226 (LaPoM)
      Lecture II     6 March, 5:00 PM, Room 226 (TPF)
      Lecture III     8 March, 4:15 PM, Room 226 (LaPoM)

Lectures on FOLDS II.
FOLDS, first-order logic with dependent sorts, was introduced by me in a 1995 monograph ( It is explained in outline in the paper "Towards a categorical foundation of mathematics" published in Springer Lecture Notes in Logic, no.11, 1998. FOLDS is intended as the formal language for a foundational system  based on higher dimensional categories, analogously to ordinary first-order logic in ZFC set theory. The syntax of FOLDS is simple; it is related, although not identical, to earlier formalisms by Per Martin-Lof and John Cartmell. However, unlike the latter, FOLDS is a fully model-theoretical language, with a general Tarskian semantics and an accompanying model theory.  Its main feature is a replacement of ordinary (Fregean) equality (as in "logic with equality") by a new, signature-dependent notion of FOLDS equivalence. In its most direct application, FOLDS equivalence takes the role of isomorphism of ordinary model theory; but it also specializes, in the appropriate contexts, to equivalence of categories, biequivalence of bicategories, etc. The most important application of FOLDS equivalences appear in my definition of a universe called "The multitopic category of all multitopic categories" (1999 and 2004; the site above).

In the lectures, I will try to describe the concepts and their theory through examples, rather than general formulations. The project of the new "categorical" foundation has as its aim the establishing of a self-contained formal theory of totalities that is workable, and also fundamentally different from ordinary set-theory insofar it should be free from smallness considerations of the Cantorian type. This project is far from being completed, and the audience is invited to join in the investigation of the several precise mathematical questions as well as the more general philosophical aspects of the project.

13 March (Wednesday) 5:00 PM  Room 226
Tamás Ullmann
Department of Modern Philosophy, Institute of Philosophy Eötvös University, Budapest
A filozófia mint praxis
(Philosophy as practice)
Az európai filozófia története a filozófia tudományossá és elméletivé válásának története. Ennek természetesen megvannak a pozitív eredményei, de vannak negatívumai is. Ez utóbbiak közül talán a legfontosabb az, hogy az antikvitásban még magától értetődő praktikus és terápiás jelleg eltűnt a filozófiai hagyományból. A filozófiai gyakorlatot felváltotta a gyakorlati filozófia (etika, morálfilozófia, axiológia, cselekvéselmélet), a terápiás jelleg pedig elméleti kritikává vált. A XX. században megjelentek olyan irányzatok, amelyek arra tettek kísérletet, hogy a filozófiát ismét gyakorlattá, filozófiai lélekgyakorlattá tegyék, vagyis a terápia fogalmát mintegy visszahódítsák a pszichológiától. Az előadás ennek a tendenciának a hátterét, lehetőségeit és jövőjét igyekszik tisztázni.

20 March (Wednesday) 5:00 PM  Room 226
Attila Molnár
Department of Logic, Institute of Philosophy
Eötvös University, Budapest
Mass and Modality
The Logic and Theory of Relativity group lead by Andréka, H. and Németi, I. developed several axiom systems for relativity theory to investigate it within mathematical logic.

One of the simplest and most commonly used axiom system is an axiom system of kinematics, the so-called SpecRel. Although this axiom system is very simple, it implies all the main predictions (theorems) of special relativity theory. However, as it is proposed by the group in many articles, sometimes the classical first-order logic framework of SpecRel does not seem to be sufficient to give back the appropriate physical meaning. For example, the main axiom of SpecRel, the axiom which is about the possibility of sending out light signals, states that there could be a photon which crosses certain points. This "could be" indicates some kind of notion of possibility, which is barely accessible from a classical first-order logic.

This problem becomes more serious when we try to expand the system SpecRel by certain dynamical axioms (to get SpecRelDyn). For example, we would like to postulate that for every observer, everywhere, any kind of possible collision is realizable. It is worth to investigate this type of axioms, because this way leads to an experimental understanding of the notion of possibility.

We will investigate axiom systems of special relativity based on modal logic, which is the standard tool for formally handle dynamical notions – such as performing a (thought-) experiment, for instance "send out a light signal" or "realize a collision".

Our axiom systems will be built with the following goals:
- Give a plausible but formal notion of possibility/experimentation based on the informal explanations of the classical SpecRel and SpecRelDyn.
- Save the theorems and the ideas of their proofs from SpecRel and SpecRelDyn.
- Show that in a modal framework the mass can be explicitly defined essentially in the language of kinematics. This can be viewed as the formal interpretation of the operational definition of mass.